title: Diagnostic accuracy of arterial line blood gas measurements as an estimate of arteriovenous fistula recirculation.
abstract: OBJECTIVE
  We studied the diagnostic accuracy of blood gas determination as a novel method for the estimation of arteriovenous fistula (AVF) recirculation (RC).
  
  
  METHODS
  In 25 patients on chronic haemodialysis, with failure of a previously well functioning native AVF (mean two-needle urea-based RC: 41 ± 10%), arterial line (AL) as well as a peripheral vein (PV) blood samples drawn by the end of a 4 h haemodialysis session, before and after the surgical repair of their AVF.
  
  
  RESULTS
  Compared to PV samples, patients with RC had significantly higher AL blood pCO2 and pO2 values (P < 0.001) and lower AL blood pH and K(+) values (P < 0.001), findings that were reversed after the surgical restoration of adequate AVF function. On regression analysis, urea RC values were correlated positively with AL pCO2 values (r = 0.683, P < 0.001) and negatively with AL pH values (r = 0.896, P < 0.001). AL pCO2  > 40 mmHg was shown to have the best sensitivity and AL pH < 7.25 the best specificity. RC index, that is, the AL pCO2 /pH ratio, was found to have superior test characteristics compared to pH and pCO2 (sensitivity 95% and specificity 88% for values >5.5) making it a powerful diagnostic as well as screening tool.
  
  
  CONCLUSIONS
  We propose the regular AL blood gas measurement as a novel method of AVF function surveillance and RC diagnosis. AL blood pH < 7.25, pCO2  > 40 mmHg and RC index > 5.5, escorted by rather high pO2 and low K(+) by the end of dialysis session, but probably earlier as well, signify an important RC (>20%) and warrant further investigation of AVF patency.
authors.affiliation: 'Evangelismos' Dialysis Unit, Veria, Greece; Medical School, Aristotle University, Thessaloniki, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Kirmizis
authors.forename: Ourania
authors.initials: O
authors.lastname: Kougioumtzidou
authors.forename: Pantelis
authors.initials: P
authors.lastname: Vakianis
mesh_terms: D000368:Aged; D001166:Arteriovenous Shunt, Surgical; D002245:Carbon Dioxide / Q000097:blood*; D005260:Female; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D006435:Renal Dialysis
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen
keywords: access surveillance; acidosis; arteriovenous fistula; blood gases; recirculation; vascular access